My overall view is that folks just don't know how to relate to the set up.
The real determining factor is the difference of an IR, i.e., individual runner induction v. a single plenum system on a V8 engine.
I like to say that it just is not going to make your 351 into a 427 no matter what you think.
Dyno tests have definitely shown that there is actually more horsepower gains available with a single four barrel carburetor on a single plenum intake manifold available.
That simply does not tell the entire story though. You don't drive a Dyno. It is only a tuning tool that puts you in the private corporate box in the ball park.
The rest is up to you to apply the data to.
The MAIN benefit to the Weber induction system is that it is much more responsive to throttle openings then the single four barrel can be and secondarily, isn't subject to the loss of fuel delivery caused by severe cornering and braking like Holley's are.
Optimum intake runner length from carb throttle opening to the intake valve opening is obtained with the IR intake and the eight accelerator jets are mostly responsible in combination to that effect.
Consider that the early 1969 Boss 302 Trans Am racing induction of two Holley Dominator carbs on an individual runner intake manifold have exactly the same "issues" as the Webers do.
That is caused by the intake manifold design, not the carburetors.
I have actually found that the best combination of maximum naturally aspirated V8's is a 2x4ble carb on an equal length runner intake using vacuum secondary carbs.
On Fords, that combination only exists in two set ups. 1) the dual 4 big block FE like the 427's and 2) the C60A small block "Trans Am" intake.
The small block intake being much better engineered since it actually has equal length runners much like a tunnel ram would but has dual plenums which are connected together.
So there it runs all day on a single set of two barrel throttles to about 3,000rpm's, then begins to open the second carb throttles like it is a double pumper, then allows the vacuum secondaries to open on engine demand. So the induction is completely progressive.
My small block is a 347 in a 302. It is using two Holley 1850 carbs. So with the linkage it responds like a 600 Holley double pumper with boosters because of the vacuum secondaries. Those only open as the engine demands.
Some racers use an adage that the Holley carb size should be about twice the size of the cubic inch displacement. In that case that would be around a 700cfm carb.
I have run a single Holley 750dp, e.e., a 4779, on the Cleveland which is just a hair too big.
I have run a Holley 2x4 list 3300,3301 combination on the 347 which would put it at about 725cfm combination which works really well.
That considering the adage seems to explain things.
Another racer's adage which you might find interesting is that the dyno horsepower is going to show about 2x's the measured headflow.
So in the case of the 347, those are AFR heads and their test numbers show 296cfm at .550" lift so about 592hp which seems about right.
My A3 heads on the Cleveland show about 330cfm at .600". So about 660hp on that one.
Personally I looked for an intake manifold like that for the 9.2" Cleveland but it was never made by Ford Engineering. One has never emerged. You would have to adapt the Shelby 2x4 Boss 302 intake to a 351 Cleveland and that would really be a Rube Goldberg combination unfortunately of a VERY expensive intake (if you could even find one).
So to clean up the idle on the Weber 48ida system, you need to abandon the carbs and go to an EFI replacement. There are Weber look a-like EFI throttle bodies and at least two CPU systems available to control that.
One by Holley and one by FAST which is the Edelbrock in disguise. Both will clean up the idle and both will maximize the induction as seen by AI.
There is a difference in feel between the EFI and the Webers and the main complaint about the EFI is just that it is too smooth in comparison but in many instances the desired improvements searched for are really just a re-examination of how to reinvent the wheel. Maybe looking for the pot of gold at the end of the rainbow?
Incidentally, the air corrector to use with a 150 fuel main calculates to 171 air, so the answer is try a 170 air or a 175 air on a Cleveland.
A 210 air would be for a 289 set up. It has a different proportion of fuel to air and they do not translate back and forth to each other.
I am not telling you this from theory but from actual seat of the pants testing that I DID, ME so ANYONE else telling you otherwise is trying to sell you a bridge with a toll booth so good luck on that. 
As an aside on that testing, most of the witnesses to those events have passed or moved away. The Police involved have retired so the stories of that are now just MOSTLY contained in local "folklore". Fortunately for EVERYONE involved the Statute of Limitations HAS expired! 